Both single and fractionated CNS irradiation in a genetically altered mouse model were tested, and have shown similar results with reduction in amyloid plaque number, size and volume. Moreover, the fractionated studies the investigators have demonstrated statistically significant improvement in the treated mice using the Morris Water Maze Test when compared to control non-treated animals, an effect which held up whether the animals were adolescent, mature or aged (up to 18 months old).